Čupona, Ǵorǵi and Celakoski, N. (1996) “FREE OBJECTS IN SOME VARIETIES OF GROUPOIDS”, Matematichki Bilten, 20(1), pp. 5–16. Available at: https://bilten.smm.org.mk/index.php/bilten/article/view/1561 (Accessed: 14 August 2026).